Advances in biotechnology have made it possible to take a gene sequence which is responsible for the expression of a valuable protein in one organism, such as the human gene for insulin, and introduce it into another organism which expresses the valuable protein, for example into a fermentation broth or milk. Unfortunately, it is usually very difficult and expensive to isolate the valuable protein from the other components of the expression system. Isolation and purification are main contributors to the cost of the products.
It is known in the brewing industry that certain insoluble substances, such as silica gels, silica hydrogels and silica cogels, are "sorbants" which absorb, adsorb or entrap proteins and as such are useful in removing undesirable proteins from beer. The proteins are removed from the beer quickly and inexpensively.
The Raible U.S. Pat. No. 3,436,225 discloses a process for removing undesirable proteins from beer with a combination of silica gel and aluminum silicate.
The Barby et al. U.S. Pat. No. 3,617,301 discloses a process for the treatment of beer to reduce its tendency to form haze on storage which comprises adding to the beer a silica hydrogel. The patent also discloses that various other insoluble sorbants, such as bentonite, active carbon, nylon, polyvinyl pyrrolidone, as well as, other silica containing compounds have been previously used for this purpose and that they are to a greater or lesser extent effective.
The Hau U.S. Pat. No. 4,636,394 discloses the use of a combination of two distinct amorphous silicas to remove chill haze precursor proteins from beer.
The Mizerak et al. U.S. Pat. No. 4,528,198 discloses the use of sorbants, including silica hydrogel, to selectively remove yeast lethal factors from malt extract.
The Welsh et al. U.S. Pat. No. 4,684,530 discloses a method of removing haze-forming proteins from wine using inorganic oxide-silica cogels. The patent also discloses the regeneration and recycling of the cogel.
None of the above described patents disclose any method by which a valuable protein is removed from a broth and recovered.
There is a need for a simple method of removing and recovering valuable proteins from complex solutions, such as fermentation broths and milk, and also a need for a method of determining which valuable proteins can be removed from such solutions by that method.